Variable dashpots are intended to allow the driving characteristics of a vehicle to be adapted to the varying road conditions. Additional adjustable bypass valves are associated with vibration-suppression valves in the piston. They can be controlled with manually activated switches or by an electronic paragraph that varies the vibration suppression in accordance with varying input parameters.
German 3 405 315 A 1 discloses a variable dashpot for vehicles in which an electric motor of the type called a micromotor is accommodated in the piston rod and controls a component that varies the cross-section of the bypass. Since even such motors are fairly large, however, the piston rod must also be large. The motor occupies space otherwise employed for backing up the vibration-suppression fluid, and the device must be expanded or extended. These known electric motors also have the drawback of too long a response time for automated controls.
The object of the present invention in to improve a variable dashpot to allow continuous and highly dynamic adjustments to the cross-section of the bypass in a dashpot of acceptable dimensions.
This object is attained in accordance with the invention by providing a cylinder and piston in which vibration-suppressing fluid fills the cylinder and the piston has vibration-suppressing valves. The piston separates the cylinder into two compartments which communicate through a bypass cross-section which is adjustable. The adjustment is produced through an electric motor which has stator windings held in a recess of the piston rod that is attached to the piston. The piston rod is made of magnetic material. The rotor of the motor has permanent magnets and is held in a bore in the stator.
The rotor is arranged so as not to rotate more than 360.degree. in relation to the stator, by a rotation limiter which is provided with stops. The adjustment of the bypass cross-section is carried out with an adjusting component that is integrated into the rotor. The rotor, moreover, may be provided with a thread that engages another thread for moving the adjustment component which cannot rotate back and forth. A position sensor may be associated with either the rotor or the adjusting component.
The invention has several advantages. Very few components are employed, few enough to ensure simple assembly of a system for adjusting the open cross-section of a bypass. The embodiment in accordance with the invention is highly reliable and, due to its small size, can be employed in a highly dynamic system. A variable dashpot can easily be employed in the space usually occupied by a non-variable dashpot. This is a particular advantage in conjunction with industrial-scale manufacture.